I am NOT interested in buying a bike now, and upgrading to a different one later: I want to buy one bike once and use it forever.
Good luck. At $800, that's a tough deal for a new bike. There IS a spectrum of getting what you pay for in MTB. Is a $8K MTB twice as good as a $4k? probably not. Is a $2K one more than twice as good as an $800 one? More likely.
I find I'm better off buying better bike up front, and spending less in maintenance later. ie: My last mountain bike came with junky rims, and I ended up replacing one when the non-serviceable hub fell apart. And that was a $1200 MSRP bike! New MTB cost more up front, but will last much longer.
A Rockshox Reba or Recon would be reasonable for a front fork, yes.
I'd DEFINITELY go Hardtail for your description. An $800 FS bike? Your'e asking for CHEAP junky suspension components.
I find hydraulic disc brakes are worth the expense to me.